August 22, 1966

MEMORANDUM for Chief, Research Projects Office

Flight 1-66-111 was flown on August 11, l966, by John B. McKay for the purpose of obtaining data for a) micrometeorite collection, b) horizon scanner, c) high altitude sky brightness, d) rarefied gas flow, e) electrical loads, and, f) wing tip pod acceleration.

The maximum velocity was 5150 fps (3511 mph and a Mach number of 4.72) at an altitude of 147,000 feet. The maximum altitude reached during the flight was 250,000 feet.

Acceptable data were obtained on all experiments except the high altitude sky brightness, on which a fuse failed just prior to engine shutdown.

The major malfunctions which occurred during the flight were electrical power transients which in turn caused the inertial and SAS systems to malfunction, and the failure of the sky brightness experiment fuse. To correct these problems, the following courses of action are being taken: a) environmental testing of the sky brightness experiment, and b) changing of the number 2 AC bus voltage regulator and inspecting the generators.

Prior to this flight a hardware fit check of the PMR launch monitor experiment was performed. The check proved satisfactory with only minor discrepancies being encountered.

Flight Profile

The radar track and profile for this flight are shown in figure 1 and a time history of the flight is shown in figure 2.

The launch was a Delamar Lake launch from 45,000 feet altitude. The launch was normal with approximately 16° of right roll being experienced. Engine light was also normal and 100% power attained in 2.7 seconds. Rotation after launch initially peaked at 15° angle of attack then lowered to 10° until the planned q of 38° was reached 3 seconds later than planned because the rotation angle of attack was a degree lower than the planned 11° angle of attack rotation.

Engine shutdown was accomplished at 5150 fps as planned after 84.0 seconds of powered time. These conditions resulted in a peak altitude of 250,000 feet as was planned. (see figure 2)

The entry alpha during q buildup averaged approximately 18° which was 2° less than the planned 20° angle of attack. The maximum acceleration during the entry was 4.1 "g" instead of the planned 5.0 "g". The average normal acceleration during the entry and recovery was less than 3 "g". These conditions resulted in an entry dynamic pressure of approximately 2000 psf, which was 860 psf higher than the planned 1140 psf.

The landing approach and main gear touchdown were normal, however, just at nose gear touchdown the pilot indicated he felt a sharp left roll pulse and then the airplane continued in a left hand turn during roll out. This was verified by a check of the lakebed.

Micrometeorite Collection

This experiment was activated during the flight, by the pilot at approximately 200,000 feet altitude. The experiment extended out of the right hand wing pod nose cone and proceeded through its automatic timing cycle as planned. However, due to the improper setting of the micro switch actuator gear, by the experimenter, only the last three of the six collector surfaces were exposed.

The experiment remained extended for 116.5 seconds, and upon descending through 180,000 feet the pilot initiated the experiment to retract. The experiment retracted into the wing pod normally and remained for the remaining duration of the flight.

The collector box is awaiting pick up by the experimenters.

Horizon Scanner

Preliminary analysis of data indicate that the horizon scanner functioned as planned. Data acquisition for a period of 77.0 seconds, starting at a point 6 seconds after shutdown, was accomplished.

Data are being analyzed by the experimenter in preparation for the next flight.

Sky Brightness

Approximately 9.5 seconds before engine shutdown a 5-amp slow-blow fuse failed, resulting in the loss of data on this flight for this experiment. The fuse was replaced for a postflight checkout and the experiment functioned properly. Since no immediate reason for the failure could be found it was requested of the experimenter to perform an environmental test on the experiment.

The environmental test is now in progress at the FRC facilities. The longitudinal acceleration portion of the test has been completed as required, with negative results. Temperature and altitude tests remain to be completed.

The decision not to fly the experiment on the next flight has been made because the cause and solution to this failure has not been resolved.

Rarefied Gas Flow

There has been no indication of problems on the rarefied gas flow (pace transducer) experiment for this flight. Data are presently being analyzed.

Electrical Loads

Data for the survey of the electrical loads on the APU's was recorded on this flight. A preliminary analysis indicates only a portion of the data recording channels operated during the flight. A comparison of data on this flight and flight 1-65-108 show a similar power situation existed on both flights, when the inertial system computer and the airplane damper system malfunctioned. A detailed analysis of these data are in progress in an effort to determine what caused the power transients.

Wing Tip Pod Accelerometer

To determine the "g" loadings experienced by the wing tip pods during flight an accelerometer was mounted in the right hand wing tip pod. These measurements are required for a study being conducted to determine if the present weight limitations imposed on the pods can be increased to accommodate future wing pod experiments.

Data obtained during flight are being analyzed.

Operational Discrepancies

During the BCS check the windshields of the X-15 iced over from the water vapor present in the steam from the BCS rockets. The ice dissipated prior to launch. This problem was believed to be due to the fact there were no nose BCS heaters installed in the airplane.

A small leak was noted in one of the top BCS rockets after priming. The leak finally stopped before launch.

The B-52 compass was off during the prelaunch portion of the flight.

The pilot indicated that angle of sideslip was reading 2 1/2° to the right prior to launch and zeroed out after launch. Telemetry data verified this to be correct.

The power transients experienced during flight caused several malfunctions. A power transient approximately 11.5 seconds prior to engine shutdown caused an inertial system computer malfunction. Another transient 2 seconds later failed the pitch and roll dampers. Eight seconds later the roll damper was reengaged. Approximately 8 seconds after engine shutdown the pilot was able to reengage the pitch damper and reset the inertial system computer.

The ASAS came on when the dampers malfunctioned; after the dampers were reengaged the ASAS was turned off and the dampers remained engaged for the remainder of the flight.

Possible causes of these power transients are being investigated and several courses of action for correcting this problem are being pursued. The airplane power system is being checked for possible short circuits. The #2 AC regulator has been changed. Power checks will be made with all systems operating. Experiment #l9 is being removed from the airplane because a short is suspected as evidenced by the blown fuse. Environmental tests are being conducted to check the experiment for altitude, temperature and acceleration effects.

The airplane swung sharply to the left after landing. The landing gear shock-strut service was suspected as a contributing cause.

Instrumentation Discrepancies

The following parameters did not function during flight:

APU power A phase #1

APU power B phase #1

APU power C phase #1

APU power A phase #2

APU power B phase #2

The following parameters did not calibrate during the data zero .and calibrate sequences:

Upper Vertical Stabilizer position

Pitch Horizontal Stabilizer position

Upper Speed Brake position

Roll Horizontal Stabilizer position

SAS Pitch-Roll left hand cylinder displacement

SAS Yaw Cylinder displacement

A portion (approximately 25 to 30 inches) of three internally recorded flight records (0-42-36C, 0-12-36C, and A-B-3M) were dark due to accidental exposure to the light during their development process .

Traces on P-61-2 started to blur during engine operation and were not legible prior to engine shutdown.

These discrepancies are being investigated to determine their cause.
 
 

E. J. Adkins, Chief

X-15 Research Project Office